Cellular communications systems are well known in the art. In a typical cellular communications system, a geographic area is divided into a series of regions that are referred to as “cells,” and each cell is served by a base station. The base station may include baseband equipment, radios and antennas that are configured to provide two-way radio frequency (“RF”) communications with mobile subscribers that are geographically positioned within a “coverage area” served by the base station. In many cases, the coverage area may be divided into a plurality of “sectors,” and separate antennas are provided for each of the sectors. Typically, these antennas are mounted on a tower or other raised structure, with the radiation beam(s) that are generated by each antenna directed outwardly to serve the respective sector.
A common wireless communications network plan involves a base station serving a coverage area using three base station antennas. This is often referred to as a three-sector configuration. In a three-sector configuration, each base station antenna serves a 120° sector of the coverage area. Typically, a 65° azimuth Half Power Beamwidth (HPBW) antenna provides coverage for a 120° sector. Three of these antennas provide 360° coverage. Typically, each antenna comprises a linear phased array antenna that includes a plurality of radiating elements that are arranged as a single column of radiating elements. Other sectorization schemes may also be employed. For example, six, nine, and twelve sector configurations are also used. Six sector sites may involve six directional base station antennas, each having a 33° azimuth HPBW antenna serving a 60° sector. In other proposed solutions, a single, multi-column phased array antenna may be driven by a feed network to produce two or more beams from a single phased array antenna. Each beam may provide coverage to a sector. For example, if multi-column phased array antennas are used that each generate two beams, then only three antennas may be required for a six sector configuration. Antennas that generate multiple beams are disclosed, for example, in U.S. Patent Publication No. 2011/0205119 and U.S. Patent Publication No. 2015/0091767, the entire content of each of which is incorporated herein by reference.
Increasing the number of sectors increases system capacity because each antenna can service a smaller area and therefore provide higher antenna gain throughout the sector and/or allow for frequency reuse. However, dividing a coverage area into smaller sectors has drawbacks because antennas covering narrow sectors generally have more radiating elements that are spaced wider apart than are the radiating elements of antennas covering wider sectors. For example, a typical 33° azimuth HPBW antenna is generally twice as wide as a typical 65° azimuth HPBW antenna. Thus, cost, space and tower loading requirements may increase as a cell is divided into a greater number of sectors.